Oxygen generating canisters for closed circuit breathing apparatus



Sept. 8, 1964 R. M. BOVARD ETAL OXYGEN GENERATING CANISTERS FOR CLOSED CIRCUIT BREATHING APPARATUS 2 Sheets-Sheet 1 Filed Sept. 26, 1958 no a e 0 09 006 doo t INVENTORS. ROBERT m. 50VABO,&= 04.25) a. ans/($0M Sept. 8, 1964 R. M. BOVARD ETAL 3,148,034

OXYGEN GENERATING CANISTERS FOR CLOSED CIRCUIT BREATHING APPARATUS 2 Sheets-Sheet Filed Sept. 26, 1958 INVENTORS. ROBERT M. BOVARD, 9:. C935) 5. JHCKSON.

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United States Patent "ice 3,148,034 OXYGEN GENERATING CANISTERS FOR CLQSED CIRCUIT BREATHING APPARATUS Robert M. Bovard, Evans City, and Carey B. Jackson, Zeiienopie, Pa, assignors, by mesne assignments, to Mine Safety Appliances Company, Pittsburgh, Pa, a corporation of Pennsyivania Filed Sept. 26, 1958, Ser. No. 763,756 4 Claims. (@l. 23-281) This invention relates to closed circuit breathing apparatus, and more particularly to the canisters in which carbon dioxide is removed from exhaled air and oxygen is added to it.

In closed circuit breathing apparatus the air exhaled by the user is purified and oxygen is added so that he can rebreath the air. The circuit is not open to the atmosphere. The usual chemical material for removing carbon dioxide and water from the exhaled breath and adding oxygen to it is K0 although any of the alkali metal peroxides and superoxides can be used. The chemical is activated by moisture from the breath. As breathing continues, the chemical offers more and more resistance because the chemical particles soften and fuse together. This results in requiring either excessive effort to breathe or replacement of the canister.

It is among the objects of this invention to provide closed circuit breathing apparatus, in which the useful life of the oxygen generating canister is prolonged and in which increasing breathing resistance is retarded.

In accordance with this invention a plurality of chambers, usually about two, are filled with oxygen generating material of the type that is activated by moisture. Each chamber has an inlet and an outlet. The inlets are connected with the exhalation conduit of the breathing apparatus and the outlets are connected with the inhala tion conduit. Each chamber is provided with means requiring a different breathing effort to draw air through it. Breathing therefore takes place first through the chamber offering the least resistance. As the breathing resistance in that chamber increases, or as breathing effort increases due to exertion, breathing will occur through the other chamber where the resistance to breathing will not become too great until long after the first chamber has become inactive.

The invention is illustrated in the accompanying drawings; in which FIG. 1 is a plan view of a canister embodying our invention;

FIG. 2 is a central vertical section through the canister; and

FIG. 3 is a somewhat schematic view of a modification, but with the canisters shown in longitudinal section.

Referring to FIGS. 1 and 2 of the drawings, the metal housing 1 of an air purifying canister is provided in the center of its upper end with an inlet port 2, to which the outer end of an exhalation tube 3 is secured. The other end of the tube opens into a conventional breathing mask (not shown). The center of the lower end of the canister housing is provided with an outlet port 4 that is connected to the inlet of an inhalation tube 5. The other end of this tube is connected to the mask. The housing is nearly filled with oxygen generating material 6, such as K0 or another alkali metal peroxide or superoxide. The body of chemical particles is supported on a screen 7 and filter 8, which in turn are supported a short distance above the bottom of the housing by means of a corrugated perforated spacer 9 to provide an air space beneath the entire chemical body. At the top of the housing there also is a perforated spacer it? to provide an open area above the chemical. The top of the oxygen 3,i48,34 Patented Sept. 8, 1964 producing material is covered by a screen 11 and a filter 12.

It is a feature of this invention that the canister is divided lengthwise into two chambers 14 and 15 of substantially equal size by means of a vertical partition 16 extending through the canister housing from one end to the other. It will be seen that both ends of the two chambers thus formed communicate with the inlet and outlet of the canister. One chamber is provided with means requiring more effort to breathe through it than through the other chamber. Most suitably, this means consists of a second filter 17 below top filter 12. By having two filters at one end of chamber 15, it requires considerably more effort to breathe through that chamber than through the other one.

When the canister is first put into use all, or substantially all, breathing will take place through the chamber offering the lesser breathing resistance, provided breathing is normal so that the chamber can handle it. The moisture in the breath will react with the chemical and cause it to absorb carbon dioxide and liberate oxygen. As breathing continues, the chemical particles will soften and start to fuse together and thereby gradually increase the resistance which the chemical offers to passage of air through chamber 14. As this resistance increases, greater effort will have to be put forth in order to breathe, and this greater effort will cause air to be drawn through the other chamber too. The time will come when the breathing resistance of the first chamber will become too great for further use, but breathing can continue for some time through the second chamber. Consequently, the life of this canister is much longer than that of a conventional canister having only one chamber to breathe through.

Another place where this canister has a definite advantage is when the user first breathes normally for a while and then, because of exertion, requires more oxygen and therefore exerts more effort in breathing. During the normal breathing the chamber with the smaller breathing resistance will take care of his needs. Under exertion, however, his increased breathing effort will cause him to breathe through both chambers. By the time his period of exertion is over, the resistance of chamber 14 may be excessive, but he will be used to breathing through chamber 15 and can continue to breathe through it without discomfort.

It will be observed that the problem here is different than that encountered with gas masks, where the chemical reaction is of a different type.

In the embodiment shown in FIG. 3 instead of using a two chamber canister with an added filter to increase resistance through one chamber, a plurality of canisters are shown. Two or more can be used. All of the canisters are single chamber units and would have the same breathing resistance if it were not changed by means of valves. Thus, the canisters 21, 22 and 23 are arranged in parallel and their inlet ports are connected to a header 24 that may be connected to a tube 25 inside of a breathing bag 26. The end of the bag remote from the inlet of this tube is connected to the exhalation tube 27 of a face mask 28. The outlet ports of the canisters are also connected with a common header 29, that is joined to the inhalation tube 30 of the breathing apparatus. Both ports of canister 21 are unimpeded, but one port of each of the other canisters is normally closed by a check valve.

The valves 32 and 33 may be in the inlet or outlet ports. Those shown are in the outlet ports and may take various forms. A simple one is illustrated, in which each valve member is normally held closed by a tension spring connected to it. One spring is stronger than the other so that it will require more effort to open valve 33 than valve 32. With this apparatus, normal breathing occurs through the unvalved canister 21 first. As the breathing resistance in that canister builds up or as exertion causes a greater breathing efiort, the valve 32 for canister 22 will be opened and allow breathing through that canister. With still greater exertion or breathing resistance in the first two canisters, the breathing effort will become great enough to open valve 33 of the third canister 23. After the exertion is over so that breathing otherwise could return to normal, the user will be accustomed to the effort; required to breathe through the third canister and will be able to continue to breathe through it without discomfort even though the resistance of the other two canisters has become so great that air no longer passes through them.

According to the provisions of the patent statues, we have explained the principle of our invention and have illustrated and described What we now consider to represent its best embodiment. However, we desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

We claim:

1. In a closed circuit breathing apparatus, at least two chambers filled with oxygen generating material and each having an inlet and an outlet for connection with an exhalation conduit and an inhalation conduit respectively, said chambers forming parts of parallel breathing circuits, and pressure drop creating means other than said material initially providing different resistance to air flow through the different chambers, the difference in pressure drop created by said means being sufficiently great to insure that normal breathing will take place substantially entirely through the chamber offering the least resistance and until the breathing effort increases to a point where it will overcome the breathing resistance oifered by the chamber that initially had greater pressure drop.

2. In a closed circuit breathing apparatus, at least two chambers filled with oxygen generating material and each having an inlet and an outlet for connection with an exhalation conduit and an inhalation conduit respectively, said chambers forming ports of parallel breathing circuits and a filter in one chamber initially providing enough more resistance to air flow through that chamber than through the other one to insure that substantially all breathing will take place through said other chamber first.

3. In closed circuit breathing apparatus, a housing having an inlet in one end and an outlet in its opposite end, the inlet and outlet being adapted to be connected to an exhalation conduit and an inhalation conduit respectively, a body of oxygen generating material filling the housing but spaced a short distance from its ends, a partition extending lengthwise through the housing to divide it into two parallel chambers containing said material and cornmunicating with said inlet and outlet, and a filter in one chamber providing more resistance to air flow through that chamber than through the other one until said material in the latter chamber has been partially expended.

4. In closed circuit breathing apparatus, at least two canisters disposed in fixed relation to each other and containing oxygen generating material and each having an inlet port and an outlet port for connection with an exhalation conduit and an inhalation conduit respectively, said canisters forming ports of parallel breathing circuits, and a normally closed check valve in one of said ports offering material resistance to opening, whereby breathing will first take place through the other canister, the valve being unseatable by air pressure against one side of it when the breathing resistance in said other canister rises and increases the breathing efiort enough to overcome said resistance to opening.

References Cited in the file of this patent UNITED STATES PATENTS 2,218,604 Dill Oct. 22, 1940 2,220,706 Cantin Nov. 5, 1940 2,469,367 Burgess et al. May 10, 1949 2,889,210 Bovard June 2, 1959 FOREIGN PATENTS 183,336 Switzerland June 16, 1936 19,575 Netherlands Feb. 15, 1929 

1. IN A CLOSED CIRCUIT BREATHING APPARATUS, AT LEAST TWO CHAMBERS FILLED WITH OXYGEN GENERATING MATERIAL AND EACH HAVING AN INLET AND AN OUTLET FOR CONNECTION WITH AN EXHALATION CONDUIT AND AN INHALATION CONDUIT RESPECTIVELY, SAID CHAMBERS FORMING PARTS OF PARALLEL BREATHING CIRCUITS, AND PRESSURE DROP CREATING MEANS OTHER THAN SAID MATERIAL INITIALLY PROVIDING DIFFERENT RESISTANCE TO AIR FLOW THROUGH THE DIFFERENT CHAMBERS, THE DIFFERENCE IN PRESSURE DROP CREATED BY SAID MEANS BEING SUFFICENTLY 